This invention relates to the gasification of sulfur-containing liquid hydrocarbonaceous fuel or a slurry of sulfur-containing solid carbonaceous fuel. More specifically it relates to the removal of sulfur-containing gases from the raw effluent synthesis gas stream produced in a refractory lined free-flow gas generator.
As supplies of petroleum gradually diminish sulfur-containing heavy liquid hydrocarbonaceous fuel and/or sulfur-containing coal which is America's most abundant form of fossil fuel will play an increasingly major role in providing for the nation's energy requirements. One ton of coal contains the same amount of energy as three to four barrels of crude oil. Accordingly, in the future it will become necessary to produce an increasing fraction of liquid and gaseous fuels from these sulfur-containing comparatively low cost fuels. The synthesis, reducing, and fuel gases produced from these sulfur-containing materials contain a comparatively high e.g. from about 0.1 to 2.0 mole % of H.sub.2 S and COS. The desirability for removing at high temperature a major share of the sulfur present in synthesis gas as generated in the Partial Oxidation Gasification Process is widely recognized. In particular, removing sulfur from syngas at high temperatures would improve combined cycle thermal efficiency and decrease costs by eliminating the need for cooling product gases prior to scrubbing. When the synthesis gas is burned as fuel in a gas turbine, it may be unnecessary to remove the last trace of sulfur. Energy savings such as are possible through a high temperature (circa 1000.degree. F.) desulfurization process can outweigh the need to get an extremely low sulfur content fuel gas. The gas produced by this invention may be used with or without further processing and/or purification as a gaseous fuel or as feedstock for the catalytic synthesis of liquid fuels.
Synthesis gas, fuel gas, and reducing gas may be produced from coal by well known gasification processes. For example, coassigned U.S. Pat. Nos. 3,544,291 and 4,289,502 respectively relate to a process for the partial oxidation of slurries of coal, and to an apparatus for producing cleaned and cooled synthesis gas by the partial oxidation of solid carbonaceous fuel. The subject invention is superior to the mode wherein iron oxide is mixed with the fuel feedstock to the gasifier, such as described in coassigned U.S. Pat. No. 4,668,428, since calcium can accept more sulfur at the lower temperature in the radiant cooler of the subject invention. Further, the thermal energy produced by the sulfur removal reaction may be now recovered in the radiant cooler.
The use of an iron-containing additive to react with sulfur-containing gases in a stream of synthesis gas is described in coassigned copending U.S. patent application Ser. No. 07/090,822, now U.S. Pat. No. 4,778,485 which is incorporated herein by reference. However, it was unexpectedly found that at the lower temperatures resulting after cooling the process gas stream to solidify the slag, as provided by the invention described herein, calcium is more potent than iron for capturing sulfur in-situ. For example, at a temperature of 1500.degree. F., 98.2% of the sulfur may be removed as CaS in comparison with 87.4% of the sulfur removed as FeS.